Field of the Invention
The present invention relates to a spectrum analysis apparatus and a calibration method capable of calibrating stray light.
Background Art
In the related art, spectrum analysis apparatuses capable of calibrating stray light are known. One of such spectrum analysis apparatuses is disclosed, for example, in JP-A-2014-48232.
JP-A-2014-48232 discloses an optical characteristic measurement apparatus (spectrum analysis apparatus) including a spectroscope, a detector configured to receive light split by the spectroscope, a detachable high-cut filter configured to cut wavelength components shorter than a predetermined wavelength from light incident on the spectroscope, and a processing unit configured to output results detected by the detector. The optical characteristic measurement apparatus disclosed in publication of JP-A-2014-48232 is configured to observe short wavelength components, which ideally should have been removed from light having passed through the high-cut filter and entering the spectroscope but actually have been detected therein by the detector to identify long wavelength components (stray light) incident on the detector from routes other than a normal route. The identified long wavelength components are then eliminated from the result of measurement, so that correction for eliminating an effect of stray light is achieved.
In addition, in the related art, a calibrating method in which monochromatic light rays associated with individual detection elements provided in a detector are sued as incident light to measure and acquire for each of the monochromatic light rays intensity ratios between incident light passing through a normal route and being observed by an intended detection element and stray light incident on and passing through abnormal routes and thus observed by a plurality of unintended detection elements.
However, with the optical characteristic measurement apparatus (spectrum analysis apparatus) in the JP-A-2014-48232 publication, although most part of the effect of the wavelength components passed through the high-cut filter on the wavelength components cut by the high-cut filter are eliminated, relationship between the wavelength components in the incident light and the wavelength components that appear as stray light cannot be figured out. Therefore, there remains a problem that the effect of stray light may not be eliminated accurately from a wavelength distribution in a result of measurement.
When the monochromatic light rays associated with the individual detection elements are used as incident light for calibration, measurement needs to be performed by the number of times of measurement corresponding to the total number of the detection elements. In addition, since the bandwidths of the monochromatic light rays are very narrow and thus a sufficient amount of light may not be obtained, measurement needs to be continued for a long time to obtain sufficiently accurate and reliable intensity ratios between the intensity of incident light passing through the normal route and incident on the intended detection elements and the intensity of the stray light passing through abnormal routes and incident on the intended detection elements. Consequently, the time required for measurement for calibration becomes disadvantageously huge. Accordingly, correction for eliminating the effect of stray light accurately from the wavelength distribution in a result of measurement in a short time is disadvantageously difficult.
In order to solve the above-described problems, it is an object of the invention to provide a spectrum analysis apparatus capable of performing correction for eliminating an effect of stray light accurately from a wavelength distribution in a result of measurement in a short time.